From: Kirill Tkhai <ktkhai@parallels.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kirill Tkhai <tkhai@yandex.ru>, Oleg Nesterov <oleg@redhat.com>,
<linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
"Vladimir Davydov" <vdavydov@parallels.com>
Subject: Re: [PATCH RFC] sched: Revert delayed_put_task_struct() and fix use after free
Date: Thu, 16 Oct 2014 13:51:55 +0400 [thread overview]
Message-ID: <1413453115.24793.73.camel@tkhai> (raw)
In-Reply-To: <1413453002.24793.72.camel@tkhai>
В Чт, 16/10/2014 в 13:50 +0400, Kirill Tkhai пишет:
> В Чт, 16/10/2014 в 11:43 +0200, Peter Zijlstra пишет:
> > On Thu, Oct 16, 2014 at 12:16:44PM +0400, Kirill Tkhai wrote:
> > > В Чт, 16/10/2014 в 09:59 +0200, Peter Zijlstra пишет:
> > > > On Thu, Oct 16, 2014 at 01:46:07AM +0400, Kirill Tkhai wrote:
> > > > > > --- x/kernel/sched/fair.c
> > > > > > +++ x/kernel/sched/fair.c
> > > > > > @@ -1165,7 +1165,7 @@ static void task_numa_compare(struct tas
> > > > > >
> > > > > > rcu_read_lock();
> > > > > > cur = ACCESS_ONCE(dst_rq->curr);
> > > > > > - if (cur->pid == 0) /* idle */
> > > > > > + if (is_idle_task(cur) || (curr->flags & PF_EXITING))
> > > > > > cur = NULL;
> > > > > >
> > > > > > /*
> > > > > >
> > > > >
> > > > > Looks like, we have to use the same fix for task_numa_group().
> > > >
> > > > Don't think so, task_numa_group() is only called from task_numa_fault()
> > > > which is on 'current' and neither idle and PF_EXITING should be
> > > > faulting.
> > >
> > > Isn't task_numa_group() fully preemptible?
> >
> > Not seeing how that is relevant.
> >
> > > It seems cpu_rq(cpu)->curr is not always equal to p.
> >
> > It should be afaict:
> >
> > task_numa_fault()
> > p = current;
> >
> > task_numa_group(p, ..);
> >
> > And like said, idle tasks and PF_EXITING task should never get (numa)
> > faults for they should never be touching userspace.
>
> I mean p can be moved to other cpu.
>
> tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);
>
> tsk is not p, (i.e current) here.
Maybe I undestand wrong and preemption is disabled in memory fault?
next prev parent reply other threads:[~2014-10-16 9:51 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-15 12:31 [PATCH RFC] sched: Revert delayed_put_task_struct() and fix use after free Kirill Tkhai
2014-10-15 15:06 ` Oleg Nesterov
2014-10-15 19:40 ` Oleg Nesterov
2014-10-15 21:46 ` Kirill Tkhai
2014-10-15 22:02 ` Kirill Tkhai
2014-10-16 7:59 ` Peter Zijlstra
2014-10-16 8:16 ` Kirill Tkhai
2014-10-16 9:43 ` Peter Zijlstra
2014-10-16 9:50 ` Kirill Tkhai
2014-10-16 9:51 ` Kirill Tkhai [this message]
2014-10-16 10:04 ` Kirill Tkhai
2014-10-17 21:34 ` Oleg Nesterov
2014-10-16 7:56 ` Peter Zijlstra
2014-10-16 8:01 ` Peter Zijlstra
2014-10-16 22:05 ` Oleg Nesterov
2014-10-17 21:36 ` [PATCH] sched/numa: fix unsafe get_task_struct() in task_numa_assign() Oleg Nesterov
2014-10-18 8:15 ` Kirill Tkhai
2014-10-18 8:33 ` Kirill Tkhai
2014-10-18 19:36 ` Peter Zijlstra
2014-10-18 21:18 ` Oleg Nesterov
2014-10-19 8:20 ` Kirill Tkhai
2014-10-18 20:56 ` Oleg Nesterov
2014-10-18 23:13 ` Kirill Tkhai
2014-10-19 19:24 ` Oleg Nesterov
2014-10-19 19:37 ` Oleg Nesterov
2014-10-19 19:43 ` Oleg Nesterov
2014-10-20 9:03 ` Kirill Tkhai
2014-10-20 9:13 ` Peter Zijlstra
2014-10-20 10:36 ` Kirill Tkhai
2014-10-20 9:00 ` Kirill Tkhai
2014-10-19 21:38 ` Peter Zijlstra
2014-10-20 8:56 ` Kirill Tkhai
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